1. Field of the Invention
The present invention relates to a bridge between a Peripheral Component Interconnect Express interface and a Universal Serial Bus device, and particularly to a bridge that can be applied between a Peripheral Component Interconnect Express interface and a Universal Serial Bus 3.0 device.
2. Description of the Prior Art
A Peripheral Component Interconnect Express (PCI-E) interface is one kind of Peripheral Component Interconnect (PCI) interface computer bus. The PCI-E interface follows the present PCI programming concepts and communications standards, but is based on a faster serial communication system. In a PCI-E standard, a single lane data transmission speed of PCI-E 1.0 is 2.5 Gbps, but a single lane data transmission speed of PCI-E 2.0 is from 2.5 Gbps up to 5 Gbps. In addition, motherboard slots of the PCI-E 2.0 can be backwards-compatible with interface cards of the PCI-E 1.x, and interface cards of the PCI-E 2.0 can also be backward-compatible with motherboards of the PCI-E 1.x to utilize data transmission speeds provided by the motherboards of the PCI-E 1.x.
The Universal Serial Bus (USB) 3.0 specification is the third version of the USB standard. The USB 3.0 specification can support full-duplex data transmission service, and a data transmission speed of the USB 3.0 specification can be up to 5 Gbps, which is ten times a data transmission speed (480 Mbps) of the USB 2.0 specification, so the USB 3.0 device can significantly reduce time for data transmission and power consumption of data transmission. In addition, the USB 3.0 device can be backwards-compatible with a USB 2.0 device. The USB 3.0 device has 8 inner wires, with wire VBUS and wire GND acting as power supply wires, and the other 3 pairs of wires acting as data transmission wires. In the 3 pairs of wires, two data transmission wires are wires D+, D− compatible with the USB 2.0 specification and another two data transmission wires are wires SSRX, SSTX for the USB 3.0 specification.
In the prior art, the USB 3.0 device can communicate with a PCI-E interface through a port of a bridge. Although the USB 3.0 device can support a 5 Gbps data transmission speed, a data transmission speed of a single lane of the PCI-E interface is also 5 Gbps. Therefore, if the bridge is coupled to more than one USB 3.0 device, a sum of data transmission speeds of all USB 3.0 device coupled to the bridge is limited to 5 Gbps due to the data transmission speed (5 Gbps) of the single lane of the PCI-E interface, resulting in a data transmission speed of each USB 3.0 device being less than 5 Gbps.